Apparatus for detecting the three-dimensional structure of a log

ABSTRACT

An apparatus for detecting the three-dimensional structure of a log including supporting means ( 3 ) forming a holder ( 4 ) for a log ( 2 ); means ( 5 ) for detecting the log ( 2 ) lateral surface structure positioned only on one side of the log ( 2 ) placed on the holder ( 4 ); and control and processing means for receiving detection step results from them and for reconstructing the log ( 2 ) overall surface structure; and means ( 6 ) for making the log ( 2 ) rotate about one or more axes of rotation which are substantially parallel with the log ( 2 ) main direction of extension (D), the control and processing means also being operatively connected to the means ( 6 ) for making the log rotate, controlling their operation.

The present invention relates to a method and an apparatus for detectingthe three-dimensional structure of a log.

In particular, the present invention is advantageously applied in logcutting lines (FIG. 1), where the logs T are fed in sequence, positionedtransversally to their direction of extension, to a band saw S. In moredetail, a line L feeds one log T at a time to a movable carriage C whichthen moves it against the band saw S.

In plants of that type, cutting must be carried out in such a way as tooptimise the result based on the characteristics of the log. To do that,the precise structure of the log must therefore be known.

According to a first known technology (schematically illustrated in FIG.1), the log T is subjected to a three-dimensional scan upstream of thefeed line. Therefore, in the station X, the three-dimensional structureof the log is detected and the control system can identify the bestcutting pattern which can be applied. Consequently, when the log Tarrives on the carriage C, only its position in space needs to beidentified to allow correct application of the best cutting patternpreviously identified.

However, that solution is relatively complicated to produce, since itrequires a suitable detection station X in which the log must be stoppedand observed on each side with suitable three-dimensional scanners.

Alternatively, the most widespread solution involves examination of thelog T when it is already on the band saw S carriage C using a detectorR. This solution is schematically illustrated in FIG. 2, which shows theportion of the plant indicated by the arrow II in FIG. 1. Obviously, inthe solution in FIG. 2, the cutting plant does not comprise the scanningstation upstream which in contrast is present in the solution in FIG. 1.

However, this latter solution also has disadvantages. Although it issimpler to produce, it has the significant limitation that the presenceof the carriage C only allows examination of one side of the log T (asillustrated in FIG. 2). Consequently, the structure of the other sidemust be assumed.

Apart from the disadvantages of the apparatuses used in cutting plantswhich use band saws, it should be noticed that all prior art apparatusesof this type have disadvantages.

Apparatuses for detecting the three-dimensional structure of logs may bedivided into two large families, those in which the log remainsstationary, and those in which the log is fed along its main directionof extension.

In the former type of apparatuses, the main disadvantage is linked tothe need to provide a large number of detection devices in order to beable to simultaneously detect the entire lateral surface of the log.Consequently, that type of apparatus is relatively expensive.

In contrast, in the latter case, the lateral surface is usually detectedusing cross-sections one after another as the log gradually passesthrough a detection station where two or more radial detectors detecteach cross-section. In this latter case, the disadvantages are linkedboth to the need to provide two or more detectors (although smaller)and, above all, the fact that it is impossible to apply the technique tocompact, high productivity production lines in which the logs must befed positioned perpendicularly to the feed direction (if not rotatingeach log).

In this situation, the technical purpose which forms the basis of thepresent invention is to provide a method and an apparatus for detectingthe three-dimensional structure of a log which overcome theabove-mentioned disadvantages.

In particular, the present invention has for a technical purpose toprovide a method and an apparatus for detecting the three-dimensionalstructure of a log which may be used in lines in which the log is fedpositioned perpendicularly to its own direction of extension.

The present invention also has for a technical purpose to provide amethod and an apparatus for detecting the three-dimensional structure ofa log which allows the use of even a single detection device fordetecting the entire lateral surface of the log.

The technical purpose specified and the aims indicated are substantiallyachieved by a method and an apparatus for detecting thethree-dimensional structure of a log as described in the appendedclaims.

Further features and advantages of the present invention are moreapparent in the detailed description below, with reference to severalpreferred, non-limiting embodiments of a method and an apparatus fordetecting the three-dimensional structure of a log, described withreference to the accompanying drawings, in which:

FIG. 1 is a schematic plan view of a log cutting plant made according tothe prior art;

FIG. 2 is a detail of a different log cutting plant made according tothe prior art;

FIG. 3 is a front view of an apparatus for detecting thethree-dimensional structure of a log made according to the presentinvention;

FIG. 4 is a bottom view of the apparatus of FIG. 3;

FIG. 5 illustrates a log cutting plant equipped with an apparatus fordetecting the three-dimensional structure of a log made according to thepresent invention;

FIG. 6 illustrates a first embodiment of a detecting step which is partof the method according to the present invention;

FIG. 7 illustrates a second embodiment of a detecting step which is partof the method according to the present invention;

FIG. 8 illustrates a third embodiment of a detecting step which is partof the method according to the present invention;

FIG. 9 illustrates a fourth embodiment of a detecting step which is partof the method according to the present invention;

FIG. 10 illustrates a fifth embodiment of a detecting step which is partof the method according to the present invention; and

FIG. 11 illustrates a sixth embodiment of a detecting step which is partof the method according to the present invention.

With reference to the accompanying drawings, the numeral 1 denotes as awhole an apparatus for detecting the three-dimensional structure of alog 2 in accordance with the present invention.

The apparatus 1 comprises firstly supporting means 3 forming a holder 4for a log 2 to be examined and means 5 for detecting the log 2 lateralsurface structure which are pointing towards the holder 4.

In more detail, the supporting means 3 also form means 6 for making thelog 2 rotate about two or more axes of rotation (described in moredetail below) which are substantially parallel with the log 2 maindirection of extension D. In the preferred embodiment, this is achievedby making the supporting means 3 with at least one pair of motor-drivensupporting chains 7 angled at the two sides of the holder 4 andconverging below it (in front view). As shown in FIG. 3, the pair ofsupporting chains 7 therefore form V-shaped supports. However, in otherembodiments, the chains 7 which form each pair may also be spaced out,and they may or may not form a V shape when seen from the front. In theembodiment illustrated, the supporting means 3 comprise two pairs ofchains 7, but in general they may comprise a plurality of themdistributed along the length of the holder 4 to support the log 2 atseveral points.

The supporting chains 7 are looped around respective feed/return rollers8 and, as illustrated in FIG. 3, may be driven in a synchronised fashionand in the same direction to make the log 2 rotate. In FIG. 3 the log 2is schematically illustrated as a circle, therefore after rotation ofthe chains 7 it is rotated about an axis of rotation passing through thecentre of the circle. In contrast, in real conditions, the log 2 has anirregular cross-section, meaning that depending on the portion of thesection resting on each chain 7, the instantaneous axis of rotationvaries, although it always remains substantially parallel with the log 2main axis of extension (except for small angles due to the differentirregularity, such as irregularity or bump 2 a in FIG. 5, of theindividual sections resting on the support means 3 at each moment). Itshall be understood that in other embodiments the supporting androtating means 3 may be made differently to what is described above.

According to the present invention, the detection means 5 are positionedon only one side of the holder 4 (above it in FIG. 3) so that they canalways see only one part of the lateral surface of the log 2. Dependingon requirements, the detection means 5 may have any structure. Inparticular, according to what is also described below, the detectionmeans 5 may be means for detecting by laser triangulation, by detectingthe texture of the surface of the log 2, etc. Moreover, the control andprocessing means are operatively connected to the detection means 5 forcontrolling their activation, for receiving detection step results fromthem and for reconstructing the log 2 overall surface structure,according to the methods described below. The control and processingmeans are also operatively connected to the means 6 for making the logrotate, to control their operation.

In order to be able to detect the entire lateral surface of the log 2,the control and processing means are programmed to carry out theoperating steps of the method forming the subject matter of the presentinvention described in detail below. However, very briefly, the controland processing means are programmed to detect the entire lateral surfaceof the log 2 in a plurality of steps one after another, during each ofwhich only a portion of the surface is detected. However, each portiondetected is detected in such a way that it is at least partly superposedon at least one other portion detected, or to be detected, so that theoverall surface may be reconstructed by superposing the individualportions which were individually detected.

In a more complete embodiment, the apparatus 1 may comprise one or moredetectors 14 which are positioned in such a way that they can detect oneor both of the log 2 end surfaces, and operatively connected to thecontrol and processing means for operating according to the methodsindicated in detail below. However, to summarise, it may be said that inthis case the control and processing means are programmed to activatethe detectors 14 simultaneously with the detection means 5 at least fora plurality of lateral surface detection steps, so as to provide anoverall detection step result consisting of the portion of lateralsurface and one or both end surfaces. If this is done for all of thelateral surface detection steps, it is not necessary for the lateralportions detected to be partly superposed, since the end surfaces alwaysare. Consequently, the reconstructions can be performed entirely orpartly based on the information relating to the end surfaces.

Before examining the method according to this invention in detail, itmust be emphasised that the present invention also relates to a log 2cutting plant 9 comprising a band saw 10, a carriage 11 for supporting alog 2 to be cut and able to move between a first, pick up position wherea log 2 can be loaded on the carriage, and a second, cutting positionwhere the band saw 10 can cut a log 2 positioned on the carriage, and aline 12 for feeding logs 2 to be cut to the carriage 11 located in thepick up position. According to the present invention, the plant 9 alsocomprises an apparatus 1 for detecting the three-dimensional structureof the log 2 made according to what is described above and preferablypositioned downstream of the feed line 12. In particular, the apparatus1 may either be positioned between the feed line 12 and the carriage 11to form a kind of loader for the carriage 11, or it may be mounteddirectly on the carriage 11 (or may even form the carriage 11 itself).

If the apparatus 1 is an integral part of a log cutting plant 9, theremay also advantageously be means for positioning the log 2 in theoptimum cutting position (not illustrated). Said means are controlled bythe control and processing means and are designed to position the log 2on the carriage 11 in the optimum cutting position decided in themeantime, according to known methods, by the control and processingmeans, after the log 2 has been completely detected. In particular, whenthe apparatus 1 is mounted directly on the carriage 11, or coincideswith it, the apparatus also forms the positioning means. In contrast,when the apparatus 1 is located directly upstream of the carriage, thepositioning means may be either devices able to transfer the log 2 fromthe apparatus 1 to the carriage 11 with a predetermined rigid motion(such as a robot), or, more simply means for applying on the log 2 avisual positioning reference (such as a diametral line on an end face ofthe log 2). In the latter case, correct log cutting positioning isdetermined by the operator who rotates the log 2 to align the visualreference relative to a predetermined orientation (for examplevertical).

The method according to the present invention generally comprisesfirstly the operating step of making the log 2 rotate about two or moreaxes of rotation which are substantially parallel with the log maindirection of extension D. In practice, that depends, as alreadyindicated, on the methods used to carry out the step (for example,depending on the structure and operation of the apparatus 1 supportingmeans 3 as described above).

Secondly, during said rotation, the method involves detecting therelative surface structure of the log 2 at least at one lateral surfaceportion 13. The term “relative” surface structure refers to a referencesystem outside the log 2 (in practice usually integral with thedetection means 5).

It should be noticed that if two reference systems are assigned, thefirst Y to the detection means 5 and the second X to the log 2, afterlog 2 rotation the first reference system Y integral with it may,relative to the second system Y, be subject to not just a rotation, butalso a series of translations, for example after the irregularity of itssurface which gradually rests on the supporting means 3 described above.

Also, according to a first embodiment of this invention the detectionstep is repeated a plurality of times, thus detecting at least once therelative surface structure of substantially all of the points of thelateral surface of the log 2, and, at the same time, so that, at the endof all of the repetitions, each surface portion 13 detected shares atleast several points with at least one other surface portion 13detected. It should be noticed that the term surface portion 13 refersto a set of real points of the surface of the log 2, whilst the termrelative surface structure refers to detection of the surface trend of apredetermined surface portion 13.

The final basic step of the method disclosed involves combining therelative surface structures detected to reconstruct an overall surfacestructure for the log 2, and in particular combining them so that thepoints shared by the various relative surface structures are made tocoincide with each other.

In the preferred embodiment of the method according to the invention,the detection steps are repeated in such a way that during eachdetection step points of the lateral surface of the log 2 are detectedwhich are adjacent to those detected during the previous detection step.In this way, the entire lateral surface of the log 2 can be detectedduring a single log 2 rotation over itself.

Any methods may be used for carrying out the detection steps and theyare not described in detail here, being of the known type. However, inthe preferred embodiments, the detection steps are generally carried outby projecting a beam of light (preferably laser) on the surface of thelog 2 and practically instantly detecting the surface structure of theilluminated zone using the triangulation technique. In contrast, inother embodiments, detection is carried out by detecting the log 2surface texture (that is to say, its outer appearance). It is known thatthe three-dimensional appearance of an irregular object can bereconstructed according to how the appearance of the same zone of thesurface of the object varies with variations in the reciprocalpositioning between the point of observation (detection) and the zone ofthe surface detected. In other embodiments, the log surface can also bedetected using the “time of flight” technique, in which the position ofthe surface points is obtained by measuring the time taken by a lightpulse to reach the log and return to a detection sensor (this techniqueis of the known type and therefore not described in detail).Advantageously, to check the entire surface of the log rotary mirrorsmay be used, combined with interferometric techniques.

FIGS. 6 to 10 show five possible embodiments for each detection step(with reference to the positioning of FIG. 3, FIGS. 6 to 11 show a topview of the log 2) according to the first embodiment of the methoddisclosed, described here.

In general, each portion 13 detected consists of the set of linearintersections between the surface of the log 2 and a plurality ofseparate planes incident on it (in the accompanying drawings all of theplanes are perpendicular to the drawing plane, but in general they couldalso be at an angle to it). In particular, in the case of FIGS. 6 and 7the separate planes are parallel with each other and, respectively,substantially parallel with the log 2 main direction of extension D, andat an angle to it. Whilst in the former case each point of each portion13 is detected a number of times equal to the number of parallel planes(four in FIG. 6), in the latter case the distance between the differentplanes and the relative angle relative to the axis of the log 2 must besuch that for each intersection at least several points can be detectedduring a subsequent detection step. In FIG. 7 that situation is shown bythe dashed line which shows how each point at it is detected duringthree separate detection steps.

In contrast, in the case in FIG. 8, the portion 13 of the lateralsurface of the log 2 detected consists of the linear intersectionbetween the surface and a second plurality of separate planes which areat an angle both to the surface and to each other. The second pluralityof planes may be divided into a first group and a second group ofparallel planes, the planes of the first group being at an angle to theplanes of the second group. In this way the portion 13 detected forms agrid and all of the surface points are detected more than once. In thecase in FIG. 9, the detection planes are positioned side by side so thateach surface portion 13 is a longitudinal band of the log 2 surface.

Finally, in the case in FIG. 10, the portion 13 of the log 2 lateralsurface detected consists of the linear intersection between the surfaceitself and one or more first planes substantially parallel with the maindirection of extension (D) of the log (2) (or at least positioned insuch a way that they cover the entire length of the log) and one or moresecond planes substantially perpendicular to the main direction ofextension (D) of the log (2). In this way, each second plane alwayscovers the same log circumference and, with each detection step, half ofits is acquired, which can easily be superposed on the half detectedduring the next acquisition, from which it differs only by severalpoints.

Returning to the step of making the log 2 rotate, it should also benoticed that this is preferably carried out with a substantiallyconstant speed and in such a way that after a complete rotation the log2 is substantially in the starting absolute position in space. Asindicated, this may advantageously be achieved by supporting the log 2using means 6 for making it rotate, such as those illustrated in FIGS. 3and 4.

Moreover, advantageously, all of the detection steps are carried out byobserving the log 2 from the same absolute position relative to themeans 6 for making it rotate.

Finally, the step of combining the relative surface structures may beimplemented by taking the results of one detection step as the startingpoint and referring all of the others to it. In particular, once thestarting relative structure has been set (and therefore thecorresponding starting surface portion 13), it is possible to superposeon it the other relative structures corresponding to the surfaceportions 13 sharing points with the starting surface portion 13, makingthe shared points coincide. In other words, a first reference systemintegral with the starting relative surface structure is set and thecoordinates of all of the other relative surface structures aretransformed into coordinates belonging to said first reference system.Experts in the field will not have any difficulty determining thetransformation formulas to be applied by means of a comparison of thevarious relative surface structures detected.

In a more complex embodiment, the method according to the presentinvention may also comprise an additional operating step of observing atleast one end face of the log 2, as illustrated in FIGS. 4 and 11 (wherethe face is observed by a suitable detector 14).

Advantageously, the end surface detection steps are associated with atleast several of the relative surface structure detection steps.Preferably, the method disclosed may involve, simultaneously with atleast a plurality of log 2 relative surface structure detection steps(advantageously all of them), the operating step of detecting at leastone log end surface (preferably both). Advantageously, to detect the endsurfaces the technique linked to the texture described above ispreferably used.

Since the appearance of the end surface is usually well defined,knowledge of it simplifies reconstruction of the log 1 overall lateralsurface.

According to the method of implementation described here, the step ofcombining relative surface structures is also carried out based on acomparison of the end surfaces that were detected at all or several ofthe relative surface structures. This is because a comparison of thedifferent orientations in space detected for the same end surface allowsone to infer the movement performed by the log even between the twosteps for detecting the corresponding relative surface structures.

In particular, since the whole of the end surface is advantageouslydetected, a comparison between two subsequent detection step resultsreveals both the rotation to which the end surface was subjected and anytranslation of the end surface transversally to the axis of rotation.This addition to the first embodiment is particularly advantageous inthe case of lateral surfaces which are too regular and which thereforedo not provide sufficient references for correctly superposing thevarious detection step results, or, in the opposite case of surfacesthat are too ragged and irregular and so produce a lot of “noise” in thedetection step results. The second preferred embodiment of the methodaccording to this invention differs from the first embodiment describedabove only in the fact that one or both of the end surfaces is detectedfor each relative surface structure detection step, and the fact thatthere is no need for each relative surface structure (referred to thelog 2 lateral surface) to share parts with the others. The detectionstep is in fact repeated in such a way that at least several points areshared by the results of two detection steps of one or both end surfacesof the log which have been carried out simultaneously with twocorresponding detection steps for the relative surface structures. Thereconstruction is performed exclusively based on superposing the endsurfaces gradually detected.

However, preferably, for a more accurate assessment of the log 2, it ispreferable to observe both end surfaces, since the combination of theirmovements allows five of the six degrees of freedom of the log to bedescribed. The only degree of freedom which cannot be obtained is thelog movement along its main axis of extension (that is to say,perpendicularly to the end surfaces).

However, that information can be obtained by means of the detectionsteps on the lateral surface, by assessing where the log 2 ends. But ingeneral, log movements in this direction are relatively rare.

The present invention brings important advantages. First, the method andthe apparatus for detecting the three-dimensional structure of a logaccording to the present invention may be used in lines in which the logis fed positioned perpendicularly to its own direction of extension.

Secondly, they also allow the use of a single detection device fordetecting the entire lateral surface of the log, during of a singlerotation of the log.

Also, the present invention may be inserted in log cutting plants whichuse a band saw, in particular between the log feed line and the cuttingcarriage.

It should also be noticed that the present invention is relatively easyto produce and even the cost linked to implementation of the inventionis not very high.

The invention described above may be modified and adapted in severalways without thereby departing from the scope of the inventive concept.

All details of the invention may be substituted by other technicallyequivalent elements and, in practice, all of the materials used, as wellas the shapes and dimensions of the various components, may varyaccording to requirements.

1-15. (canceled)
 16. An apparatus for detecting the three-dimensionalstructure of a log comprising: supporting means (3) forming a holder (4)for a log (2); means (5) for detecting the log (2) lateral surfacestructure which during operation are pointing towards a log (2) placedon the holder (4); and control and processing means operativelyconnected to the detection means (5) for receiving detection stepresults from them and for reconstructing the log (2) overall surfacestructure; the apparatus being characterised in that the detection means(5) are positioned only on one side of the log (2) placed on the holder(4) and in that it also comprises means (6) for making the log (2)rotate about one or more axes of rotation which are substantiallyparallel with the log (2) main direction of extension (D).
 17. Theapparatus according to claim 16, characterised in that the supportingmeans (3) also form the means (6) for making the log rotate.
 18. Theapparatus according to claim 16, characterised in that the control andprocessing means are programmed to implement a method for detecting thethree-dimensional structure of a log, comprising the operating steps of:making the log (2) rotate; during said rotation, detecting the relativesurface structure of the log (2) at least at one lateral surface portion(13) using detection means (5); repeating the detection step a pluralityof times, thus detecting at least once the relative surface structure ofsubstantially all of the points at least of the lateral surface of thelog (2); and, combining the relative surface structures detected toreconstruct an overall surface structure at least for the lateralsurface the log (2); the method being characterised in that the lop (2)is made to rotate about two or more axes of rotation which aresubstantially parallel with its main direction of extension (D); thestep of rotating the log (2) is carried out by resting the lateralsurface of the log (2) on means (6) for making the log rotate, so thatthe instantaneous axis of rotation varies depending on the portion ofthe section of the log (2) resting on the means (6) for making itrotate, in such a way that after log (2) rotation a first referencesystem integral with it may, relative to the second reference systemintegral with the detection means (5), be subject to both a rotation andtranslations due to the irregularity of its surface which rests on themeans (6) for making it rotate; the detection step being repeated insuch a way that each surface portion (13) detected shares several pointswith at least one other surface portion (13) detected, and/or in such away that at least several points are shared by the results of twodetection steps of one or both end surfaces of the log which may havebeen carried out simultaneously with two corresponding detection stepsfor the relative surface structures; and also being characterised inthat the step of combining the relative surface structures is carriedout in such a way that the points shared by the various relative surfacestructures and/or the various detection step results of the end surfacesare made to coincide.
 19. The apparatus according to claim 18,characterised in that the method comprises the operating step of alsodetecting at least one log end surface simultaneously with each of thesteps for detecting the log (2) relative surface structure at least atone lateral surface portion (13), the step of combining the relativesurface structures also or only being carried out based on a comparisonbetween the end surfaces gradually detected.
 20. The apparatus accordingto claim 16, characterised in that the supporting means (3) comprise atleast one pair of motor-driven supporting chains (7) which are set at anangle at the two sides of the holder (4).
 21. The apparatus according toclaim 20, characterised in that it comprises a plurality of pairs ofsupporting chains (7) distributed along the holder (4).
 22. Theapparatus according to claim 21, characterised in that the pairs ofsupporting chains (7) form V-shaped supports.
 23. The apparatusaccording to claim 16, characterised in that it also comprises one ormore detectors (14) for detecting at least one end surface of the log(2), said detectors being operatively connected to the control andprocessing means for performing the detection simultaneously with thedetection means (5).
 24. A log cutting plant comprising: a band saw(10); a carriage (11) for supporting a log (2) to be cut and able tomove between a first, pick up position where a log (2) can be loaded onthe carriage, and a second, cutting position where the band saw (10) cancut a log (2) positioned on the carriage; and a line (12) for feedinglogs (2) to be cut to the carriage (11) located in the pick up position;an apparatus (1) according to claim 16 for detecting thethree-dimensional structure of a log (2) to be cut, positioneddownstream of the feed line (12).
 25. The plant according to claim 24,characterised in that the apparatus (1) is positioned between the feedline (12) and the carriage (11).
 26. The plant according to claim 24,characterised in that the apparatus (1) is mounted on the carriage (11).27. The plant according to claim 24, characterised in that it alsocomprises means for positioning the log (2) in the optimum cuttingposition, the positioning means being operatively connected to theapparatus (1) and to the carriage (11).
 28. The apparatus according toclaim 16, characterised in that the supporting means (3) comprise atleast one motor-driven supporting chain (7) at a side of the holder (4).29. The apparatus according to claim 28, characterised in that itcomprises a plurality of supporting chains (7) distributed along theholder (4).
 30. The apparatus according to claim 16, characterised inthat the control and processing means are operatively connected to thedetection means (5) also for controlling their activation.
 31. Theapparatus according to claim 16, characterised in that the control andprocessing means are also operatively connected to the means (6) formaking the log rotate, controlling their operation.
 32. The plantaccording to claim 27, characterised in that the apparatus also formsthe positioning means.